Company Data is the basic contact info for the Company.
Company Name - The name of your company
Address - Your company postal address
Tel - Your office phone number
Mobile - Your company mobile number
Sales email - The primary email address to send emails from
Mail host - Your outgoing mail server (Ask your web host for this)
Mail user - Your email username
Mail Password - Your email password
Currency Symbol - The currency your transactions are in
Before After - Whether your currency symbol goes before or after the value
With regards to the email settings, these will be the same details as you use in Outlook or oyur other email client.
These will be the default settings used through the site but may be over-ridden on a per-user basis in the Edit Users section.